Browsing by Author "Forman, Michele R."

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    Association between pre-diagnostic leukocyte mitochondrial DNA copy number and survival among colorectal cancer patients
    (Elsevier, 2020-10) Yang, Keming; Forman, Michele R.; Graham, Brett H.; Monahan, Patrick O.; Giovannucci, Edward L.; De Vivo, Immaculata; Chan, Andrew T.; Nan, Hongmei; Epidemiology, School of Public Health
    Background Mitochondrial DNA copy number (mtDNAcn) is considered a biomarker for mitochondrial function and oxidative stress. Although previous studies have suggested a potential relationship between mtDNAcn at the time of colorectal cancer (CRC) diagnosis and CRC prognosis, findings have been inconsistent, and no study has specifically investigated the association of pre-diagnostic mtDNAcn with CRC survival. Methods We examined the association of pre-diagnostic leukocyte mtDNAcn (measured by qPCR) with overall and CRC-specific survival among 587 patients in Nurses’ Health Study and Health Professionals Follow-Up Study. Cox models were constructed to estimate hazard ratios (HRs) and 95 % confidence intervals (95 % CIs). Results During a mean follow-up of 10.5 years, 395 deaths were identified; 180 were due to CRC. Overall, we did not observe significant associations between mtDNAcn and either overall or CRC-specific survival among all cases or by cancer location, grade, or stage. In an exploratory stratified analysis, a suggestive inverse association of mtDNAcn and overall death risk appeared among current smokers [HR (95 % CI) for 1 SD decrease in mtDNAcn = 1.50 (0.98, 2.32), P-trend = 0.06]. Reduced mtDNAcn and lower CRC-specific death risk was observed among patients aged ≤ 70.5 at diagnosis [HR (95 % CI) for 1 SD decrease of mtDNAcn = 0.71 (0.52, 0.97), P-trend = 0.03], ≤ 5 years from blood collection to diagnosis [HR (95 % CI) for 1 SD decrease in mtDNAcn = 0.65 (0.44, 0.96), P-trend = 0.03] and those consuming a low-inflammatory diet [HR (95 % CI) for 1 SD decrease in mtDNAcn = 0.61 (0.42, 0.88), P-trend = 0.009]. Conclusion no significant associations between pre-diagnostic leukocyte mtDNAcn and either overall or CRC-specific survival appeared but exploratory analysis identified potential sub-group associations.
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    Insulinemic Potential of Lifestyle Is Inversely Associated with Leukocyte Mitochondrial DNA Copy Number in US White Adults
    (Elsevier, 2020-08-01) Yang, Keming; Forman, Michele R.; Monahan, Patrick O.; Graham, Brett H.; Chan, Andrew T.; Zhang, Xuehong; De Vivo, Immaculata; Giovannucci, Edward L.; Tabung, Fred K.; Nan, Hongmei; Epidemiology, School of Public Health
    Background: Poor lifestyles have been linked to insulin insensitivity/hyperinsulinemia, which may contribute to downstream changes such as inflammation and oxidative damage and the development of chronic diseases. As a biomarker of intracellular oxidative stress, leukocyte mitochondrial DNA copy number (mtDNA-CN) has been related to lifestyle factors including diet and weight. No epidemiologic study has examined the relation between combined insulinemic potential of lifestyle and mtDNA-CN. Objectives: Our aim was to examine the association between Empirical Lifestyle Index for Hyperinsulinemia (ELIH) and leukocyte mtDNA-CN in US men and women. Methods: This cross-sectional analysis included 2835 white adults without cancers, diabetes, or cardiovascular disease at blood collection, including 2160 women from the Nurses' Health Study and 675 men from the Health Professionals Follow-Up Study. ELIH is an index based on plasma C-peptide that characterizes the insulinemic potential of lifestyle (diet, body weight, and physical activity). Relative mtDNA-CN in peripheral blood leukocytes was measured by qPCR-based assay. Results: We found a significant inverse association between ELIH and mtDNA-CN. In multivariable-adjusted linear models, absolute least squares means ± SDs of mtDNA-CN z score across ELIH quintiles in women were as follows: Q1: 0.14 ± 0.05; Q2: 0.04 ± 0.06; Q3: 0.008 ± 0.05; Q4: 0.01 ± 0.05; and Q5: -0.06 ± 0.05 (P-trend = 0.006). Means ± SDs in men were as follows: Q1: 0.25 ± 0.09; Q2: 0.23 ± 0.09; Q3: 0.07 ± 0.09; Q4: 0.02 ± 0.09; and Q5: -0.04 ± 0.09 (P-trend = 0.007). Means ± SDs in all participants were as follows: Q1: 0.16 ± 0.05; Q2: 0.07 ± 0.05; Q3: 0.01 ± 0.05; Q4: 0.01 ± 0.05; and Q5: -0.05 ± 0.05 (P-trend = 0.0004). Conclusions: Hyperinsulinemic lifestyles (i.e., higher ELIH) were associated with lower leukocyte mtDNA-CN among subjects without major diseases, suggesting that the difference in lifestyle insulinemic potential may be related to excessive oxidative stress damage.
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    Maximum and Time-Dependent Body Mass Index and Breast Cancer Incidence Among Postmenopausal Women in the Black Women’s Health Study
    (Oxford University Press, 2022) Gathirua-Mwangi, Wambui G.; Palmer, Julie R.; Champion, Victoria; Castro-Webb, Nelsy; Stokes, Andrew C.; Adams-Campbell, Lucile; Marley, Andrew R.; Forman, Michele R.; Rosenberg, Lynn; Bertrand, Kimberly A.; School of Nursing
    While excess weight is an established risk factor for postmenopausal breast cancer, consideration of maximum body mass index (maxBMI; BMI is calculated as weight (kg)/height (m)2) or BMI at a point in time relevant for breast carcinogenesis may offer new insights. We prospectively evaluated maxBMI and time-dependent BMI in relation to breast cancer incidence among 31,028 postmenopausal women in the Black Women’s Health Study. During 1995–2015, a total of 1,384 diagnoses occurred, including 787 estrogen-receptor (ER)–positive (ER+) cases and 310 ER-negative (ER−) cases. BMI was assessed at baseline and 2, 4, 6, and 8 years before diagnosis. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Compared with women with BMI <25, those with BMI ≥35 had increased risk of ER+ breast cancer but not ER− breast cancer. For BMI assessed 2 years before diagnosis, the HRs for ER+ breast cancer associated with maxBMI ≥35 and time-dependent BMI ≥35 were 1.42 (95% confidence interval (CI): 1.10, 1.84) and 1.63 (95% CI: 1.25, 2.13), respectively. The corresponding HR for time-dependent BMI assessed 6 years before diagnosis was 1.95 (95% CI: 1.45, 2.62). These findings suggest strong associations of BMI with risk of ER+ breast cancer in postmenopausal women, regardless of timing of BMI assessment.
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    Mitochondrial DNA Copy Number, Insulinemic Potential of Lifestyle, and Colorectal Cancer
    (2020-03) Yang, Keming; Nan, Hongmei; Forman, Michele R.; Graham, Brett H.; Han, Jiali; Monahan, Patrick O.
    Because colorectal cancer (CRC) is the fourth most common cancer and the second leading cause of cancer death in the US, identifying biomarkers that might inform disease prevention and early diagnosis is of great public health importance. Mitochondria are key cytoplasmic organelles containing an independent genome, i.e., mitochondrial DNA (mtDNA). It has been increasingly recognized that mtDNA copy number (mtDNAcn) is a biomarker for mitochondrial function and cellular oxidative stress. To date, the few studies that have assessed associations between mtDNAcn and CRC outcomes have yielded inconsistent findings. Further, no epidemiologic study has examined the relationship between insulinemic potential of lifestyle and mtDNAcn. Therefore, in this dissertation, three studies were conducted using data from the Nurses’ Health Study and the Health Professionals Follow-Up Study. First, the association between pre-diagnostic leukocyte mtDNAcn and CRC risk was studied in a nested casecontrol study (324 cases/658 controls). Lower mtDNAcn was significantly associated with increased risk of CRC and proximal colon cancer. That inverse association remained significant among individuals with ≥ 8 years’ follow-up since blood collection, suggesting that mtDNAcn might serve as a long-term predictor of CRC risk. Second, possible associations of pre-diagnostic mtDNAcn with overall and CRC-specific survival were examined among 587 CRC patients. MtDNAcn was not significantly associated with survival overall or in subgroups by cancer location, grade, or stage. Among current smokers, there was an inverse association between one standard deviation (SD) decrease in mtDNAcn and increased overall death risk. Among patients diagnosed at or before 70.5 years of age and those with anti-inflammatory diets, reduced mtDNAcn was associated with lower CRC-specific death risk. Lastly, the cross-sectional association between empirical lifestyle index for hyperinsulinemia (ELIH) and mtDNAcn was investigated among 2,835 subjects without major chronic diseases (cancers, diabetes, and cardiovascular diseases). A significant inverse association was found: least-squares means ± SD of mtDNAcn z-score decreased dramatically across ELIH quintiles. Overall, the findings from this dissertation will contribute to the evaluation of mtDNAcn as a potential biomarker for CRC risk and prognosis, and inform future interventions designed to reduce the insulinemic potential of lifestyle factors to preserve mitochondrial function.
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    Pre-diagnostic leukocyte mitochondrial DNA copy number and colorectal cancer risk
    (Oxford, 2019-09) Yang, Keming; Li, Xin; Forman, Michele R.; Monahan, Patrick O.; Graham, Bret H.; Joshi, Amit; Song, Mingyang; Hang, Dong; Ogino, Shuji; Giovannucci, Edward L.; De Vivo, Immaculata; Chan, Andrew T.; Nan, Hongmei; Epidemiology, School of Public Health
    Mitochondrial DNA (mtDNA) is susceptible to oxidative stress and mutation. Few epidemiological studies have assessed the relationship between mtDNA copy number (mtDNAcn) and risk of colorectal cancer (CRC), with inconsistent findings. In this study, we examined the association between pre-diagnostic leukocyte mtDNAcn and CRC risk in a case–control study of 324 female cases and 658 matched controls nested within the Nurses’ Health Study (NHS). Relative mtDNAcn in peripheral blood leukocytes was measured by quantitative polymerase chain reaction-based assay. Conditional logistic regression models were applied to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) for the association of interest. Results showed lower log-mtDNAcn was significantly associated with increased risk of CRC, in a dose-dependent relationship (P for trend < 0.0001). Compared to the fourth quartile, multivariable-adjusted OR [95% confidence interval (CI)] was 1.10 (0.69, 1.76) for the third quartile, 1.40 (0.89, 2.19) for the second quartile and 2.19 (1.43, 3.35) for the first quartile. In analysis by anatomic subsite of CRC, we found a significant inverse association for proximal colon cancer [lowest versus highest quartile, multivariable-adjusted OR (95% CI) = 3.31 (1.70, 6.45), P for trend = 0.0003]. Additionally, stratified analysis according to the follow-up time since blood collection showed that the inverse association between mtDNAcn and CRC remained significant among individuals with ≥ 5 years’ follow-up, and marginally significant among those with ≥ 10 years’ follow-up since mtDNAcn testing, suggesting that mtDNAcn may serve as a long-term predictor for risk of CRC. In conclusion, pre-diagnostic leukocyte mtDNAcn was inversely associated with CRC risk. Further basic experimental studies are needed to explore the underlying biological mechanisms linking mtDNAcn to CRC carcinogenesis.
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    The Relationship between Mammography and a Multi-factor Behavioral Index
    (Paris Scholar Publishing Ltd., 2019) Marley, Andrew R.; Gathirua-Mwangi, Wambui; Forman, Michele R.; Stump, Timothy E.; Monahan, Patrick; Champion, Victoria L.; School of Nursing
    Objective: In this study, we sought to determine whether a multi-factor behavioral index predicts mammography screening in US women. Methods: Women aged 50-75 years were enrolled in an intervention study and provided their vegetable intake, physical activity (PA), smoking, body mass index (BMI), and alcohol intake. Each factor was scored from 0 (least healthy) to 4 (most healthy) then summed to form a multi-factor behavioral index (ranging from 0-20). Selfreport and medical records were used to determine mammography screening 6-months postintervention. Logistic regression was used to estimate multivariable-adjusted odds ratios (OR) and 95% confidence intervals (CI) for the association with 6-month mammography. Results: The mean score for the multi-factor index was 11.8. An increased index score marginally predicted mammography adherence [OR = 1.05 (0.99-1.11)], with a stronger association among women receiving a doctor’s recommendation for mammography [OR = 1.12 (1.04-1.20)]. Of the independent behavioral factors, high PA [OR = 1.13 (0.99-1.30), p = .075] and low BMI [OR = 1.25 (1.04-1.51), p = .017] were marginal and significant predictors of mammography, respectively. Conclusion: Women who engaged in a healthier behavioral lifestyle were more likely to utilize mammography screening, especially if they received a physician recommendation. Physicians should encourage mammography screening as part of a healthy behavioral lifestyle.